Activity for the week of 22 April-28 April 2009

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.

KVERT reported that during 17-24 April observers from Severo-Kurilsk, about 7 km E of Ebeko, observed continued activity. Gas-and-steam plumes with some ash content rose to an altitude of 2 km (6,600 ft) a.s.l. during 17-19 April and drifted 8 km NE. On 22 April, light ash fell in Severo-Kurilsk. The Level of Concern Color Code remained at Yellow. Based on analysis of satellite imagery and information from Yelizovo Airport, the Tokyo VAAC reported that during 25-26 April ash plumes rose to altitudes of 1.2-2.1 km (4,000-7,000 ft) a.s.l. and drifted S, SW, and W.

INGEOMINAS reported that on 24 April seismicity from Galeras was similar to that seen prior to previous eruptions. Video camera views of the crater showed decreased gas emissions. The Alert Level was raised to II (Orange; "probable eruption in term of days or weeks"). Later that day, an explosive eruption was detected, prompting INGEOMINAS to raise the Alert Level to I (Red; "imminent eruption or in progress"). Incandescent blocks caused fires on the N flank. An accompanying shock wave was reported by residents up to 25 km away. A second eruption, of greater duration but less energy than the first, was detected about a half an hour later. Incandescence from both eruptions was seen from the city of Pasto (10 km E). An ash plume rose to an altitude of 10.3 km (33,800 ft) a.s.l. Ashfall was reported in areas up to 20 km W, WNW, and NW. According to a news article, populations living near the volcano were ordered to evacuate; about 200 people responded. On 25 April, ash-and-gas plumes rose 1 km above the crater. Thermal anomalies in the crater near the W flank measured 100 degrees Celsius. Ejected rocks had landed 2-3 km from the crater. The Alert Level was lowered to II.

The USGS stated that a crew from a NOAA ship working at Pagan observed continuous steam emissions from the N crater during 21-22 April. Satellite imagery analyzed by the Washington VAAC showed a diffuse plume drifting 15 km W on 23 April. On 28 April, steam emissions had decreased so the Aviation Color Code and the Volcano Alert Level were lowered to "Unassigned." There are no monitoring instruments on Pagan, thus the levels "Green" or "Normal" do not apply because background activity is not defined. Monitoring is done by satellite and ground observers.

The IG reported that seismicity from Reventador decreased to low levels on 26 March, after the seismic network had detected an earthquake swarm the same day. On 23 April, increased seismicity was characterized by long-period events interspersed with bands of spasmodic and harmonic tremor. Observers reported that steam plumes with low ash content rose to altitudes of 5.6-6.6 km (18,400-21,700 ft) a.s.l. and drifted W. Intense noises from the volcano were also reported. A thermal anomaly and a steam plume drifting 26 km WSW were detected on satellite imagery.

KVERT reported that seismic activity at Shiveluch was above background levels during 17-24 April. Based on interpretations of seismic data, ash plumes likely rose to altitudes of 4.5-5.3 km (14,800-17,400 ft) a.s.l. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome. According to observers, fumaroles were active during 16-22 and 22 April. A hot avalanche produced an ash plume that rose to an altitude of 4 km (13,100 ft) a.s.l. on 22 April.

On 25 April, increased seismicity indicated that an ash plume rose to an altitude of 7.5 km (24,600 ft) a.s.l. On 26 April, seismicity remained at high levels; continuous spasmodic tremor and a series of weak shallow earthquakes occurred. An ash explosion from the lava dome was seen on video camera. Ash emitted from a large fissure on the S flank of the lava dome produced plumes that rose to an altitude of 4 km (13,100 ft) a.s.l. and drifted ESE. The Level of Concern Color Code was raised to Red. The next day, seismicity decreased slightly but remained elevated and gas-and-steam emissions with some ash content emanated from the fissure. Based on video camera views and analysis of satellite imagery, plumes rose to altitudes of 3.5-5 km (11,500-16,400 ft) a.s.l. during 27-28 April and drifted 250 km NE. On 28 April, pyroclastic flows originated from areas near the lava dome. The Level of Concern Color Code was lowered to Orange.

CVGHM reported that seismicity from Slamet increased during 19-23 April. Diffuse white plumes rose about 50 m above the crater on 20 April. During 21-23 April, white and white-to-brownish plumes rose 50-800 m above the crater. On 23 April, the Alert Level was raised to 3 (on a scale of 1-4); people were advised not to climb the summit. According to a news article, a CVGHM volcanologist stated that lava was ejected 600 m high and ash bursts up to 112 times within a 6-hour period were detected.

Based on analysis of satellite imagery, the Darwin VAAC reported that during 23-25 April ash plumes from Barren Island rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 45-65 km NE, E, and SE.

Based on analysis of satellite imagery, the Darwin VAAC reported that during 24-25 and 28 April ash plumes from Batu Tara rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted up to 110 km in multiple directions.

SERNAGEOMIN reported that gas-and-ash plumes rose 1.5 km from Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex during 15-21 April. Seismicity remained elevated; the largest earthquakes recorded were M 4.5. The Alert Level remained at Red. Based on web camera views, analysis of satellite imagery, and pilot observations, the Buenos Aires VAAC reported that on 25 and 28 April, ash plumes rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted NE and N. According to a news article, one of about 70 people who had refused to evacuate Chaitén town (and stayed without basic services) died from hypothermia.

KVERT reported that fumarolic activity from Karymsky was seen by volcanologists during 17-24 April. Analysis of satellite imagery revealed a thermal anomaly on the volcano on 17 April. The Level of Concern Color Code remained at Orange.

CVGHM reported that diffuse white plumes from Kerinci typically rise about 300 m above the crater. On 9 September 2007 the Alert Level was raised to 2 (on a scale of 1-4) because "black smoke" plumes rose 800 m above the crater. The height of the plumes (described as "smoke") declined, but remained variable, so the Alert Level continued at 2. On 24 March 2008, ash-and-gas plumes rose to 4.3 km (14,100 ft) a.s.l. In early April 2009, increased seismicity was accompanied by ash plumes that rose as high as 600 m above the crater. During 1-20 April, light and dark plumes rose to a maximum of 500 m above the crater. On 19 April, ashfall was reported at a nearby observation post. During 19-20 April, noises indicative of an eruption were heard at the observation post. The Alert Status remained at 2 (on a scale of 1-4). Residents and visitors were advised not to enter an area within 1 km of the summit.

During 22-28 April, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha and Kupapa'u ocean entries. Occasional explosions occurred from the Waikupanaha ocean entry, and on 22 April small littoral explosions continued to build up a steep-sided cone at the Kupapa'u entry. Surface flows were present on the coastal plain. The vent in Halema'uma'u crater continued to produce a white plume occasionally tinged brown that drifted SW, N, and NE. Poor air quality in nearby communities was sometimes caused by the plume. Incandescence was intermittently seen from the vent, and sounds resembling rushing gas or rockfalls were sometimes heard in the vicinity of the crater. Various amounts of tephra, including Pele's hair, spatter, and ash, were frequently retrieved from collection bins placed near the plume.

During 17-25 April, KVERT reported that seismic activity at Koryaksky was above background levels and weak volcanic tremor was detected. Gas plumes containing a small amount of ash drifted in multiple directions during 17-18 April. On 17 and 18 April, gas-and-ash plumes were also seen on satellite imagery and drifted 100 km NE. On 20 April, a sulfur dioxide plume extended about 15 km from the volcano. During 26-28 April, seismic activity decreased to background levels; tremor was occasionally detected. The Level of Concern Color Code was lowered to Yellow.

According to a news article on 29 April, some residents on western Java (Lampung) near Krakatau have evacuated due to their observations of increased volcanic activity during the previous week. Observers reported loud blasts, lava flows, and ash plumes that rose 200-800 m above the Anak Krakatau crater. Pilots had also reported seeing ash plumes. A volcanologist from CVGHM stated that the activity did not merit an increase in the Alert level. The Alert Level remained at 2 (on a scale of 1-4).

SERNAGEOMIN reported that on 24 April ash plumes originating from an area about 700 m down the E flank of Llaima rose 500 m and drifted E. Steam emissions that accompanied the ash plumes indicated that the point of activity came from underneath the glacier. The activity lasted about 1.5 hours. The Volcano Alert Level remained at Yellow.

RVO reported that during 18-25 April white and gray plumes from Rabaul caldera's Tavurvur cone rose 0.5-1.5 km above the crater. Plumes drifted E and SE. Incandescence from the summit crater was seen at night and occasional roaring noises were reported. Ashfall was reported in Kokopo, about 20 km SE, and surrounding areas. Based on analysis of satellite imagery, the Darwin VAAC reported that on 27 and 28 April ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55 km S and 35 km SW.

AVO reported that during 22-28 April seismicity from Redoubt remained above background levels, indicating ongoing growth of the lava dome in the summit crater. On 22 April, the web camera showed steam-and-gas plumes that may have occasionally contained small amounts of ash rising from the lava dome. Views during 23-28 April were prevented by meteorological clouds. Pilots reported sulfur odors to the NE on 22 April and to the S on 28 April. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange.

MVO reported that during 17-24 April activity from the Soufrière Hills lava dome was at a low level. On 24 April, a small pyroclastic flow traveled E down the Tar River Valley. The Hazard Level remained at 3.

The Tokyo VAAC reported that a pilot saw an ash plume from Suwanose-jima on 22 April. JMA reported that an eruption the next day produced ash plumes to altitudes of 1.2-1.5 km (4,000-5,000 ft) a.s.l. and drifted E and S. On 27 April, an explosion was reported but details of a possible resultant ash plume were not. On 28 April, explosions produced plumes that rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted E.

The IG reported that during 22-28 April steam-and-gas plumes occasionally containing ash rose from Tungurahua to an altitude of 6.5 km (21,300 ft) a.s.l. and drifted SW and W. Roaring noises were reported. Ashfall was noted in areas to the SW on 21 April. During 21-22 April, incandescence from the crater was seen; incandescent blocks ejected from the crater on 22 April rolled down the flanks. On 25 April, a lahar descended the Patacocha drainage.

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The RSS (Really Simple Syndication) feed is identical to the Weekly Volcanic Activity Report minus some features including the header information (latitude and longitude and summit elevation), the Geologic Summary, and a link to the volcano's page from the Global Volcanism Program. Each volcano report includes a link from the volcano's name back to the more complete information in the Weekly Volcanic Activity Report on the Smithsonian website.

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Criteria & Disclaimers

Criteria

The Weekly Volcanic Activity Report does not necessarily include all volcanic activity that occurred on Earth during the week. More than a dozen volcanoes globally have displayed more-or-less continuous eruptive activity for decades or longer, and such routine activity is typically not reported here. Moreover, Earth's sea-floor volcanism is seldom reported even though in theory it represents the single most prolific source of erupted material. The Weekly Volcanic Activity Report summarizes volcanic activity that meets one or more of the following criteria:

- A volcano observatory raises or lowers the alert level at the volcano.
- A volcanic ash advisory has been released by a volcanic ash advisory center (VAAC) stating that an ash cloud has been produced from the volcano.
- A verifiable news report of new activity or a change in activity at the volcano has been issued.
- Observers have reported a significant change in volcanic activity. Such activity can include, but is not restricted to, pyroclastic flows, lahars, lava flows, dome collapse, or increased unrest.

Volcanoes are included in the "New Activity/Unrest" section of the Weekly Volcanic Activity Report if the activity occurs after at least 3 months of quiescence. Once a volcano is included in the "New Activity/Unrest" section, updates will remain in that section unless the activity continues for more than 1 month without escalating, after which time updates will be listed in the "Continuing Activity" section. Volcanoes are also included in the "New Activity/Unrest" section if the volcano is undergoing a period of relatively high unrest, or increasing unrest. This is commonly equal to Alert Level Orange on a scale of Green, Yellow, Orange, Red, where Red is the highest alert. Or alert level 3 on a scale of 1-4 or 1-5.

It is important to note that volcanic activity meeting one or more of these criteria may occur during the week, but may not be included in the Weekly Volcanic Activity Report because we did not receive a report.

Disclaimers

1. The Weekly Volcanic Activity Report is intended to provide timely information about global volcanism on a weekly basis. Consequently, the report is generated rapidly by summarizing volcanic reports from various sources, with little time for fact checking. The accuracy of the Weekly Volcanic Activity Report is dependent upon the quality of the volcanic activity reports we receive. Reports published in the Bulletin of the Global Volcanism Network are monthly, and more carefully reviewed, although all of the volcanoes discussed in the Weekly Volcanic Activity Report are not necessarily reported in the Bulletin. Because of our emphasis on rapid reporting on the web we have avoided diacritical marks. Reports are updated on the Weekly Volcanic Activity Report web page as they are received, therefore information may be included regarding events that occurred before the current report period.

2. Rapidly developing events lead to coverage that is often fragmentary. Volcanoes, their eruptions, and their plumes and associated atmospheric effects are complex phenomena that may require months to years of data analysis in order to create a comprehensive summary and interpretation of events.

3. Preliminary accounts sometimes contain exaggerations and "false alarms," and accordingly, this report may include some events ultimately found to be erroneous or misleading.

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An RSS (Really Simple Syndication) feed for the Weekly Volcanic Activity Report first made available on 5 March 2008 can be utilized with the aid of various free downloadable readers. The report content of the news feed is identical to the Weekly Volcanic Activity Report minus some features including the header information (latitude and longitude and summit elevation), the Geologic Summary, and a link to the volcano's page from the Global Volcanism Program. Each volcano report includes a link from the volcano's name back to the more complete information in the Weekly Volcanic Activity Report on the Smithsonian website. On 12 March 2009, GeoRSS tags were added so that the latitude and longitude for each volcano could be included with the feed.

At the end of each individual report is a list of the sources used. We would like to emphasize that the World Organization of Volcano Observatories (WOVO) website (http://www.wovo.org/) lists the regional volcano observatories that have the most authoritative data for many of these events.

A Google Earth network link for the Weekly Volcanic Activity Report was first made available on 1 April 2009. This file can be loaded into the free Google Earth software, and in turn will load placemarks for volcanoes in the current weekly report. Placemark balloons include the volcano name, report date, report text, sources, and links back to the GVP volcano page for that volcano and to the complete Weekly Report for that week.